San Francisco State University Assistant Professor of Humanities David M. Peña-Guzmán became interested in the topic of animal suicide after speaking on a panel in 2016 about whether animals in laboratories can express dissent. This got him thinking about all the different ways animals say no, which led him to the most extreme form of refusal — suicide. He began researching the subject and found a small amount of literature, mostly dating back to the 1980s and 1990s. The science on animal cognition and behavior has changed significantly since then.

“In the past 20 years, there’s been a lot of research into the emotional and mental lives of animals and a move away from just seeing them as machines that react to various forms of input,” he said. It was time for an update.

In a recent Journal of Animal Sentience article titled “Can nonhuman animals commit suicide?,” Peña-Guzmán — a philosopher by training — argues that many animals, especially cognitively sophisticated animals held in captivity, exhibit self-destructive behaviors that culminate in great bodily harm and even death. While most researchers believe only humans have the cognitive and behavioral capacity to commit suicide, there is strong scientific and philosophical evidence that animals fatally harm themselves, which then raises the question about a human's responsibility to an animal in their care.

Based on these findings, Peña-Guzmán is calling for a broader definition of suicide — one that includes animals. He calls for a “continuist view,” where suicidal behaviors are seen along a spectrum that encompasses a wide range of self-directed and self-harming activities.

According to Peña-Guzmán, scientists have found that animals experience many of the same emotional states humans suffer before attempting suicide, such as grief, depression, post-traumatic stress disorder and general helplessness. Some even exhibit conditions similar to human psychiatric disorders, such as eating disorders and anti-social, borderline and schizoid personality disorders, he added. One researcher cited in Peña-Guzmán’s article noticed that some animals will “starve themselves to death voluntarily if captured or separated from loved ones.”

One tragic example is the case of a dolphin named Kathy, who starred in the 1960s TV show Flipper. Her trainer claimed she had been depressed after spending years in captivity and that one day she simply sank to the bottom of her tank and willfully stopped breathing, committing suicide. To skeptics, Peña-Guzmán said, this could look like a case of anthropomorphism, but scientists have found that dolphins have large, complex brains and a plausible mechanism for self-annihilation. “Dolphins, unlike human beings, are not automatic breathers. Every breath they take is a conscious decision,” he said.

Some researchers may have a set of prejudices and biases about animals that prevent them from seeing the complexity of animal minds, said Peña-Guzmán. In some laboratories, ignoring an animal’s feelings may make it easier to rationalize causing them harm in laboratories because the research ultimately benefits humans, he added. Once the possibility of animal suicide is acknowledged, it could change how animals are treated in research. “If animals commit suicide while under human care, we may have to apply a strict scrutiny standard to those responsible for them,” Peña-Guzmán said.

Peña-Guzmán wants researchers to take a more open-minded approach to understanding animals, something known as epistemic humility. “Epistemic humility requires taking seriously the empirical evidence that challenges our preconceived ideas about the cognitive, emotional and behavioral capabilities of nonhuman animals,” he said. Although animal suicide hasn’t been successfully modeled in a lab, “epistemic humility dictates it can’t be ruled out altogether on the basis of current knowledge,” he added.